Development of a new multiphase equation of state for Sn*

We present the development of a new multiphase equation of state (EOS) for Sn, which consists of multiple solid phases and a liquid.  This EOS is constructed by fitting to a set of self-consistent thermodynamic data, including ambient pressure measurements,  diamond-anvil cell (DAC) results, the principal Hugoniot, shock-melting pressures, and the recent ramp compression experiment conducted at the National Ignition Facility (NIF).  To further constrain the Sn phase diagram and the thermal free energy terms, we have performed ab initio DFT/QMD calculations of Sn and incorporated them as the additional constraints.  As holdouts, we carry out preliminary hydrodynamic simulations to model recently reported gas gun experiments. Interestingly, the simulated velocimetry profiles show a large sensitivity to other non-EOS constitutive models, especially spall/cavitation treatment. In this talk we will also present our free energy models and discuss the performance of this new Sn EOS against EOS experiments.